Sulfur- and nitrogen-containing hydrocarbon feed conversion

ABSTRACT

A catalyst effective in hydrotreating and hydrocracking sulfur- and nitrogen-containing hydrocarbon feeds at low pressure. The catalyst is prepared by incorporating a platinum group metal such as palladium in ZSM-20 or in dealuminized zeolite Y. Unlike most palladium catalysts, this catalyst is not poisoned by nitrogen and sulfur in the feed.

This is a division of copending application Ser. No. 303,334, filedSept. 18, 1981 (now U.S. Pat. No. 4,377,468), which is a continuation ofSer. No. 005,066, filed Jan. 22, 1979 (now abandoned).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to catalytic conversion of hydrocarbon feedscontaining sulfur and nitrogen containing organic compounds.

2. Description of the Prior Art

Zeolitic materials, both natural and synthetic, have been demonstratedin the past to have catalytic properties for various types ofhydrocarbon conversions. Certain zeolitic materials are ordered, porouscrystalline aluminosilicates having a definite crystalline structurewithin which there are a large number of smaller cavities which may beinterconnected by a number of channels. These cavities and channels areuniform in size. Since the dimensions of these pores are such as toaccept for adsorption molecules of certain dimensions while rejectingthose of larger dimensions, these materials have come to be known as"molecular sieves" and are utilized in a variety of ways to takeadvantage of these properties.

Such molecular sieves, both natural and synthetic, include a widevariety of positive ion-containing crystalline aluminosilicates. Thesealuminosilicates can be described as a rigid three-dimensional frameworkof SiO₄ and AlO₄ in which the tetrahedra are cross-linked by the sharingof oxygen atoms whereby the ratio of the total aluminum and siliconatoms to oxygen is 1:2. The electrovalence of the tetrahedra containingaluminum is balanced by the inclusion in the crystal of a cation, forexample, an alkali metal or an alkaline earth metal cation. This can beexpressed wherein the ratio of aluminum to the number of variouscations, such as Ca/2, Sr/2, Na, K or Li is equal to unity. One type ofcation may be exchanged either entirely or partially by another type ofcation utilizing ion exchange techniques in a conventional manner. Bymeans of such cation exchange, it has been possible to vary theproperties of a given aluminosilicate by suitable selection of thecation. The spaces between the tetrahedra are occupied by molecules ofwater prior to dehydration.

Prior art techniques have resulted in the formation of a great varietyof synthetic aluminosilicates. These aluminosilicates have come to bedesignated by letter or other convenient symbols, as illustrated byzeolite A (U.S. Pat. No. 2,882,243), zeolite X (U.S. Pat. No.2,882,244), zeolite Y (U.S. Pat. No. 3,130,007), zeolite ZK-5 (U.S. Pat.No. 3,247,195), zeolite ZK-4 (U.S. Pat. No. 3,314,752), zeolite ZSM-5(U.S. Pat. No. 3,702,886), zeolite ZSM-11 (U.S. Pat. No. 3,832,449),zeolite ZSM-12 (U.S Pat. No. 3,832,449), and zeolite ZSM-20 (U.S. Pat.No. 3,972,983) merely to name a few.

A crystalline aluminosilicate zeolite well known in the art isfaujasite. The ZSM -20 zeolite for use in the present inventionresembles faujasite in certain aspects of structure, but has a notablyhigher silica/alumina ratio than faujasite, as does of course, thedealuminized zeolite Y.

SUMMARY OF THE INVENTION

The present invention relates to the use of a hydrogenation functioncontaining synthetic crystalline zeolite ZSM-20 or dealuminized zeoliteY, or the thermally treated products thereof for sulfur- andnitrogen-containing organic compound, e.g. hydrocarbon compound,conversion. The ZSM-20 and zeolite Y compositions Y have already beenidentified, while dealuminzed zeolite Y may be prepared by the methodfound in U.S. Pat. No. 3,442,795. The catalysts may be prepared byincorporating a platinum group metal (e.g. Pd) into ZSM-20 or thedealuminized Y.

When a hydrogenation component such as palladium is incorporated intothe crystalline molecular sieve zeolites ZSM-20 or dealuminized Y (bothSiO₂ /Al₂ O₃ >6), a catalyst is produced which has the ability to

(1) hydrogenate aromatic hydrocarbons at low pressure in the presence ofsulfur and nitrogen poisons

(2) convert sulfur and nitrogen containing poisons to H₂ S and NH₃ andsaturated hydrocarbons

(3) hydrocrack hydrocarbon mixtures containing sulfur and nitrogenpoisons to lower molecular weight mixtures while substantially improvingthe quality of the material remaining in the original boiling range ofthe hydrocarbon mixture.

It is known that palladium and other Group VIII metals deposited onamorphous supports are unable to hydrogenate aromatic hydrocarbons atlow pressure in the presence of sulfur and nitrogen poisons. In additionit is known (A.V. Agafonov et al, Khimiya i Tekhnologiya Topliv i Masel,No. 6 pp. 12-14, June, 1976), that Pd deposited on NaX, NaY, Namordenite, KNaL, and KNa Erionite are also essentially inactive for theabove mentioned conversion. We have also shown that the same applies toPd/HZSM-12 and Rh H B. The only Pd zeolite known to us to possess highactivity for the above mentioned conversion are Pd Dealuminized Y (s.Agafonov et al, above) and the Pd/ZSM-20 catalyst we have prepared.

Both Dealuminized Y and ZSM-20 are, as mentioned above, materialsdescribed in U.S. Pats. Nos. 3,442,795 and 3,972,983, respectively. Inaddition, such catalysts are active and stable in hydrocracking atpressures of 500-1500 psi and 500°-700° F., whereas it is not uncommonfor such hydrocracking processes to operate at 2000-3000 psi and650°-800° F.

The original cations of the as synthesized ZSM-20 for use herein can bereplaced in accordance with techniques well known in the art, at leastin part, by ion exchange with other cations. Preferred replacing cationsinclude metal ions, ammonium ions, hydrogen ions and mixtures thereof.Particularly preferred cations are those which render the zeolitecatalytically-active, especially for hydrocarbon conversion. Theseinclude hydrogen, hydrogen precursors (e.g. ammonium ions), rare earthmetals, aluminum, metals of Groups IB, IIB, IIIB, IVB, VIB, IIA, IIIA,IVA and VIII of the Periodic Table of Elements.

The zeolites for use herein may be formed in a wide variety of particlesizes. Generally speaking, the particles can be in the form of a powder,a granule, or a molded product, such as extrudate having a particle sizesufficient to pass through a 2 mesh (Tyler) screen and be retained on a400 mesh (Tyler) screen. In cases where the catalyst is molded, such asby extrusion, the aluminosilicate can be extruded before drying or driedor partially dried and then extruded.

As in the case of many catalysts, it may be desired to incorporate thezeolite with another material resistant to the temperatures and otherconditions employed in organic compound conversion processes. Suchmatrix materials include active and inactive materials and synthetic ornaturally occurring zeolites as well as inorganic materials such asclays, silica and/or metal oxides, such as alumina. The latter may beeither naturally occurring or in the form of gelatinous precipitates,sols or gels including mixtures of silica and metal oxides. Use of amaterial in conjunction with the zeolite, i.e. combined therewith, whichis active, tends to improve the conversion and/or selectivity of thecatalyst in certain organic conversion processes. Inactive materialssuitably serve as diluents to control the amount of conversion in agiven process so that products can be obtained economically and orderlywithout employing other means for controlling the rate of reaction.Frequently, zeolite materials have been incorporated into naturallyoccurring clays, e.g. bentonite and kaolin. These materials, i.e.,clays, oxides, etc., function, in part, as binders for the catalyst. Itis desirable to provide a catalyst having good crush strength, becausein a petroleum refinery the catalyst is often subjected to roughhandling, which tends to break the catalyst down into powder-likematerials which cause problems in processing.

Naturally occurring clays which can be composited with the syntheticzeolite catalysts include the montmorillonite and kaolin family, whichfamilies include the sub-bentonites, and the kaolins commonly known asDixie, McNamee, Georgia and Florida clays or others in which the mainmineral constituent is halloysite, kaolinite, dickite, nacrite oranauxite. Such clays can be used in the raw state as originally mined orinitially subjected to calcination, acid treatment or chemicalmodification.

In addition to the foregoing materials, the present catalyst can becomposited with a porous matrix material such as silica-alumina,silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia,silica-titania as well as ternary compositions such assilica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesiaand silica-magnesia-zirconia. The matrix can be in the form of a cogel.A mixture of these components could also be used. The relativeproportions of finely divided crystalline zeolite, e.g. ZSM-20, andinorganic oxide gel matrix vary widely with the crystallinealuminosilicate content ranging from about 1 to about 90 percent byweight and more usually in the range of about 2 to about 70 percent byweight of the composite.

In general, organic compounds may be catalytically converted in thepresence of the present zeolite catalyst material, including the productof thermal treatment thereof, over a range of catalytic conversionconditions, including a reaction temperature of from about 100° F. toabout 1200° F., preferably from about 400° F. to about 1000° F., areaction pressure of from atmospheric to about 10,000 psig, preferablyfrom about atmospheric to about 3,500 psig, and a hydrogen/organiccompound ratio of from 0 to about 20,000 scf/bbl, preferably from 0 toabout 10,000 scf/bbl. When the conversion is conducted in a flowapparatus, e.g. a down-flow reactor, or under conditions comparable tothose existing in a flow apparatus, the liquid hourly space velocity(LHSV) should be maintained at between about 0.1 hr⁻¹ and about 10 hr⁻¹.When the conversion is conducted in a batch apparatus, e.g. a stirredbatch reactor, or under conditions comparable to those existing in abatch apparatus, the contact time should be maintained at between about0.01 hour and about 48 hours, preferably between about 0.1 hour andabout 24 hours.

In particular, when the conversion of organic compound by the presentmethod is olefin polymerization, catalyst conversion conditions shouldbe maintained within certain critical ranges, including a temperature offrom about 100° F. to about 800° F., preferably from about 400° F. toabout 600° F., a pressure of from about atmospheric to about 4,000 psig,preferably from about atmospheric to about 2,000 psig, a LHSV (when aflow operation) of from about 0.1 hr⁻¹ to about 50 hr⁻¹, preferably fromabout 1 hr⁻¹ to about 10 hr⁻¹, and a contact time (when a batchoperation) of from about 0.1 hour to about 48 hours, preferably fromabout 0.5 hour to about 24 hours and a hydrogen/hydrocarbon (i.e.olefin) ratio of from about 50 scf/bbl to about 10,000 scf/bbl,preferably from about 500 scf/bbl to about 5,000 scf/bbl.

When the conversion is olefin or paraffin aromatization, catalystconversion conditions should be maintained within critical ranges,including a temperature of from about 600° F. to about 1200° F.,preferably from about 800° F. to about 1000° F., a pressure of fromabout 50 psig to about 10,000 psig, preferably from about 100 psig toabout 1,000 psig, a LHSV (when a flow operation) of from about 0.1 hr⁻¹to about 10 hr⁻¹, preferably from about 1 hr⁻¹ to about 5 hr⁻¹, acontact time (when a batch operation) of from about 0.1 hour to about 48hours, preferably from about 1 hour to about 24 hours and ahydrogen/hydrocarbon (i.e. olefin or paraffin) ratio of from about 50scf/bbl to about 10,000 scf/bbl, preferably from about 100 scf/bbl toabout 1,000 scf/bbl.

Further, when the conversion of organic compound by the present methodis cracking, catalytic conversion conditions should be maintained withincertain critical ranges, including a temperature of from about 700° F.to about 1200° F., preferably from about 800° F. to about 1000° F., apressure of from about atmospheric to about 200 psig, a LHSV (when aflow operation) of from about 0.5 hr⁻¹ to about 50 hr⁻¹, preferably fromabout 1 hr⁻¹ to about 10 hr⁻¹, and a contact time (when a batchoperation) of from about 0.01 hour to about 24 hours, preferably fromabout 0.1 hour to about 10 hours. When the conversion is hydrocracking,catalyst conversion conditions should be maintained within somewhatdifferent ranges, including a temperature of from about 400° F. to about1000° F., preferably from about 500° F. to about 850° F., a pressure offrom about 500 psig to about 3500 psig, a LHSV (when a flow operation)of from about 0.1 hr⁻¹ to about 10 hr⁻¹, preferably from about 0.2 hr⁻¹to about 5 hr⁻¹, a contact time (when a batch operation) of from about0.1 hour to about 10 hours, preferably from about 0.2 hour to about 5hours and a hydrogen/hydrocarbon ratio of from about 1000 scf/bbl toabout 20,000 scf/bbl, preferably from about 3,000 scf/bbl to about10,000 scf/bbl.

In order to more fully illustrate the nature of the invention and themanner of practicing same, the following non-limiting examples arepresented.

The ZSM-20 starting material was made in accord with the procedure setout in Example 1 below, while the Pd/Mg/ZSM-20 and Pd/Mg/Dealuminized Ywere made in accord with procedures set forth in Examples 2 and 3 below.

EXAMPLE 1

A mixture of

193.7 gm Tetraethylorthosilicate

7.9 gm Sodium Aluminate

291 ml 2.8N Tetraethylammonium hydroxide and

72 gm Water

which gives the following mole ratios

SiO₂ /Al₂ O₃ =30

H₂ O/SiO₂ =15

OH/SiO₂ =0.90

Na/SiO₂ =0.09 and

TEA/SiO₂ =0.88

was aged for 3 days at 25° C. in a 300 ml polypropylene bottle and thencrystallized for an additional 18 days at 100° C. under staticconditions to give crystalline ZSM-20 in 90% purity with a SIO₂ /Al₂ O₃mole ratio of 8.66.

EXAMPLE 2 5% Pd/Mg/ZSM-20

The TEA, Na ZSM-20 was exchanged with 1 molar MgCl₂ at reflux overnight,washed until free of CL⁻, and air dried at 120° C. The magnesiumexchanged ZSM-20 was then reslurried in distilled H₂ O, an aqueoussolution of Pd(NH₄)₄ Cl₂ was added dropwise, stirred overnight at 40°C., washed free of Cl⁻, air dried at 140° C., and then air calcined at500° C. for four hours. Elemental analysis of the calcined catalystshows that Pd exchange was quantitative.

A product was obtained having the oxide composition:

    ______________________________________                                        5% Pd/Mg/ZSM-20                                                                      wt %        meq/gm                                                     ______________________________________                                        PdO      6.2           1.0                                                    MgO      3.3           1.6      3.24                                          Na.sub.2 O                                                                             1.98          0.64                                                   SiO.sub.2                                                                              74.00                                                                Al.sub.2 O.sub.3                                                                       14.50         2.84                                                   SiO.sub.2 /Al.sub.2 O.sub.3 = 8.66                                            ______________________________________                                    

EXAMPLE 3 5% Pd/Mg/Dealuminized Y

500.3 gm (2068 meq Al) of Na Y (SiO₂ /Al₂ O₃ =4.9) was slurried in 1300ml deionized H₂ O. 233.07 gm (692 meq) Na₂ EDTA was added and the slurryheated to reflux while stirring. 262 ml 5N HCl (1310 Meq H⁺) was addedto the refluxing stirred slurry at a rate of 3.4 ml/hr so as to remove31.7% of the framework aluminum and give a SiO₂ /Al₂ O₃ ratio of 7.1.Elemental analysis of the dealuminized material gave a SiO₂ /Al₂ O₃ratio of 6.8 and Na/Al ratio of 0.96 indicating the presence of somenon-framework aluminum. The dealuminized sample was found to be 86%crystalline when compared to the original Na Y starting material.

50 gm of the dealuminized Na Y was exchanged 3 times (4, 22, 4 hours)with 300 ml 1N MgCl₂ at reflux, given an intermediate calcination at500° C. and given one additional exchange treatment for 4 hours usingthe same procedure. Elemental analysis shows that 73% of the Na had beenexchanged by Mg.

15 gm of the Mg exchanged-dealuminized Y was then slurried in 100 mldeionized H₂ O and a 50 ml aqueous solution containing 0.75 gm Pd asPd(NH₃)₄ ⁺⁺ was added dropwise and stirred for 20 hours @60° C.

The Pd exchanged material was washed until free of Cl⁻, dried at 120° C.and calcined at 500° C. for 4 hours. The calcined catalyst contained5.2% Pd, was tan in color, and showed no evidence of metallic Pd byX-ray.

A product was obtained having the oxide composition:

    ______________________________________                                        5% Pd/Mg/Dealuminized Y                                                       wt %           meq*/gm                                                        ______________________________________                                        5.9            0.98                                                           3.25           1.62     3.52                                                  2.84           0.92                                                           71.1                                                                          16.9           3.34                                                           SiO.sub.2 /Al.sub.2 O.sub.3 = 7.15                                            ______________________________________                                         *Milliequivalents of ionic species per gram of dehydrated catalyst.      

EXAMPLES 4-6

Tetralin containing 700 ppm S as benzothiophene was converted over theabove catalysts and Ht-500E, a commercially available hydrotreatingcatalyst which was used as a control in this work. The results obtainedare summarized below.

    ______________________________________                                                                          Example 6                                            Example 4     Example 5  HT500E                                      Catalyst Pd/Mg/ZSM-20  Pd/Mg/DalY NiMo/Al.sub.2 O.sub.3                       ______________________________________                                        T °F.                                                                           460      480      500      600                                       LHSV     1.0      1.0      1.0      1.0                                       Pressure 500      500      500      500                                       PSIA                                                                          Tetralin 94       100      100      11                                        Conv.                                                                         Decalin  80       55       79       70                                        Select.                                                                       C.sub.10 Selec-                                                                        >95      >95      >95      100                                       tivity                                                                        ______________________________________                                    

From the above data it is obvious that the ZSM-20 based catalyst is moreactive than the catalyst based on dealuminized Y (the best knowncatalyst of prior art) and is much more active than the commercialNiMo/Al₂ O₃ catalyst.

EXAMPLES 7-9

Identical experiments were performed except that 500 ppm N as quinolinewas added to the sulfur-containing feed with the following results:

    ______________________________________                                                                          Example 9                                             Example 7    Example 8  Ht-500                                      Catalyst  Pd/Mg/ZSM-20 Pd/Mg/DalY NiMo/Al.sub.2 O.sub.3                       ______________________________________                                        T °F.                                                                            625          625        630                                         LHSV       1            1          1                                          Pressure  750*         500        500                                         Tetralin Conv.                                                                          75            30         13                                         Decalin Select.                                                                         68            86         61                                         C.sub.10 Selectivity                                                                    99           >95        100                                         ______________________________________                                    

Again the ZSM-20 catalyst was the most active, *Increaseing pressurefrom 500 to 750 psi has a significant activating effect.

EXAMPLES 10-12

As further examples, a 475°-725° F. Arab Light gas oil containing 1.09%S, 60 ppm N and 13.32% H, was reacted over the three catalysts at 1.0LHSV, 750 psi, and 6000 scf/bbl H₂ with the following results:

    ______________________________________                                                                Example 11                                                                              Example 12                                             Example 10   Pd/Mg/    Ht-500                                      Catalyst   Pd/Mg/ZSM-20 DalY      NiMo/Al.sub.2 O.sub.3                       ______________________________________                                        Time on Stream                                                                           450                210     215                                     (Hrs.)                                                                        T °F.                                                                             600                635     648                                     420.sup.+  Conversion                                                                    29.7               31.7    <1                                                 14.39                                                              % H in C.sub.5.sup.+  Prod.                                                                            14.31                                                                              14.30   13.85                                              14.23                                                              % S in C.sub.5.sup.+  Prod.                                                              .002               .12     .07                                     ______________________________________                                    

In this case the zeolite catalysts were able to produce productscontaining much more hydrogen than those produced over the NiMo/Al₂ O₃catalyst. Again, the ZSM-20 based catalyst being more active than thatbased on dealuminized Y.

In summary, from all of the foregoing, it has been found that thehydrogenation activity and selectivity of the Pd/ZSM-20 catalyst at lowpressure in the presence of sulfur and nitrogen is not an expected,general characteristic Pd/zeolite type catalyst.

What is claimed is:
 1. A process for effecting catalytic hydrogenationof aromatic hydrocarbons, at a pressure of between 500 psig and 750 psigand a temperature of between about 460° F. and 625° F., of an aromatichydrocarbon charge containing sulfur-and nitrogen-containing organiccompounds which comprises contacting a mixture of said charge andhydrogen with a catalyst comprising a palladium/Mg/ZSM-20, wherein saidZSM-20 has a silica to alumina ratio greater than 6.